An organic light emitting display (OLED) is a hot topic in the present flat panel display research field. Compared with a liquid crystal display, OLED has advantages of low power consumption, low production cost, self-luminescent, broad viewing angle, and fast response speed and so on. At present, in the display field of a mobile phone, a PDA and a digital camera and the like, OLED has started to replace a traditional LCD display screen. The pixel driving circuit design is a core technical content of the OLED display, and has important research significance.
Unlike a thin film transistor liquid crystal display (TFT-LCD) that utilizes a stable voltage to control luminance, OLED belongs to a current-driven display and needs a stable current to control light emitting.
Due to process manufacturing and device aging and so on, in the traditional 2T1C driving circuit (comprising two thin film transistors and one capacitor), the threshold voltage of the driving TFT of respective pixel points has non-uniformity, which results in that the current flowing through OLED of each pixel point changes, so that the display luminance is non-uniform, thereby influencing the display effect of the entire image.